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Conclusion:
We demonstrated the feasibility of making and
using gel phantoms for the assessment of isotropic diffusion
kurtosis to use in the characterization of early stage prostate
cancer treated with prostate brachytherapy. We have shown
that the rectified noise floor, which exists in standard
magnitude data, increases the systematic error of the
diffusion coefficients D and K. Further studies are in progress
to minimize the impact of noise floor in DKI.
EP-1879
Difference between PET and RMI fusion on delineation
variability for liver metastases
R. Tanguy
1
Centre Léon Bérard, Radiation Therapy, Lyon, France
1
, A. Gaumier
1
, M.P. Sunyach
1
, G. Beldjoudi
1
Purpose or Objective:
Liver metastases delineation on the
dosimetric computed-tomography (CT) scan is associated with
high inter-observer variations. Many authors are using a
fusion of the dosimetric CT scan with a magnetic resonance
imaging (MRI) to define the target volume and lower the
inter-observer variations. In our center we are using PET-CT /
dosimetric CT fusion or RMI / dosimetric CT fusion to
delineate liver lesions depending on physicians habits. We
wanted here to evaluate the benefit of each imaging
registration on contouring variability.
Material and Methods:
Four patients (pts) were treated with
stereotactic body radiation therapy (SBRT) for 6 liver
metastases. Each pt had a CT scan simulation, a liver-MRI and
a PET CT before treatment. Four physicians delineated the
liver lesions on the fused PET-CT and on the fused RMI. For
each pt, each physician made 2 contours on the CT scan in
the following order: first with the PET-CT fusion available
(PET/CT), then with the CT/MRI fusion available (RMI/CT).
The percentages of common contoured volumes (CCV) on
PET-CT and RMI were defined using the formula: (common
volume of all the physicians of the group /delineated volume
of the physician) x 100. The Jaccard index (ratio between
common volume and the union volume obtained using the
boolean operators) was also calculated.
Results:
The volume of the delineated lesions were (mean+/-
SD) 18.8 cc +/- 12cc vs 20.8 cc +/- 13.6 cc on PET/CT and
RMI/CT respectively (p=0.63). The common contour volume
wasn't statistically different between the two contouring
modalities with (mean+/-SD) 56.2% +/- 21.5% vs 63.34% +/-
13.9% for PET/CT and RMI/CT respectively (p=0,1) even if
there was a trend for a lesser variability for RMI fusion. The
overall Jaccard index (mean±SD) was 0.34±0.15 and
0.46±0.19 for PET/CT and RMI/CT respectively (p=0.26).
Conclusion:
A PET/CT fusion didn’t improve the volume
variation among the radiation oncologists compared to a RMI
fusion. The CCV and Jaccard index were still unsatisfying
with both PET/CT and RMI/CT fusion and we are planning to
assess the potential impact of a liver metastases contour
made by a radiologist to further improve the inter-observer
variability.
EP-1880
Validation of the use of digital camera for the prediction of
skin toxicity in breast radiotherapy
M. Poli
1
Candiolo Cancer Institute - FPO- IRCCS, Medical Physics,
Candiolo, Italy
1
, S. Bresciani
1
, A. Miranti
1
, A. Di Dia
1
, A. Maggio
1
, M.
Gatti
2
, P. Gabriele
2
, M. Stasi
1
2
Candiolo Cancer Institute - FPO- IRCCS, Radiotherapy,
Candiolo, Italy
Purpose or Objective:
Skin reactions are one of the most
common side effects in breast cancer patient treated with
radiotherapy. In this work a preliminary validation of the use
of a digital camera, as a cheap and easy tool for early
prediction of acute skin side effects, is presented.
Material and Methods:
Twelve patients undergoing breast
radiotherapy were photographed once a week with a digital
camera system, composed of a reflex Canon 30D (CMOS
sensor, 8.2 Megapixels) and a Tamron SP AF17-50mm f/2.8
XR. Patients were treated with two different techniques:
conventional 3DCRT with Varian TrueBeam STx linac (8
patients) and Tomotherapy HD (4 patients). All photographic
shots were acquired in manual-raw mode with the same
exposure and white balance setup. Shots were converted in
the best quality format available (TIFF) and post-processed in
Lab color space (Color Space Converter plugin for ImageJ,
NIH) to amplify color differences. From the channel related
to image redness (a*), a skin redness level was obtained for
each photographed fraction by using ImageJ. In particular,
two regions of interest (ROIs) were identified: one inside the
treatment field (IF) and one out-of-field (OF). Redness value
histograms, related to each ROI, was acquired, plotted and
used to evaluate the degree of skin redness level. ROI-
redness (RR) was defined as the maximum redness value of
the related histogram. The OF ROI defined the redness
baseline. IF RR values were plotted as a function of the
corresponding fraction number and fitted with a line; the
slope of this of this line is defined as RR gradient. For each
patient, skin toxicity, evaluated with RTOG criteria, was
compared to the RR gradient.
Results:
G1 and G2 toxicities were experienced by 10 and 2
patients, respectively. A strong relation between RR gradient
and skin toxicity was found: an average RR gradient of
(0.24±0.09) redness/fraction was found for G1 patients, while
an average RR gradient of (0.54±0.15) redness/fraction was
found for G2 patients. Due to the small statistical power of
the present sample, p-values were not evaluated. The trend
of the fit may be correctly assessed since the first 2 weeks of
treatment. Changes in skin redness were found when
comparing patients treated with conventional 3DCRT with
those treated with Tomotherapy. In fact, several hot spots
were noticed for the conventional treatments rather than for
the volumetric irradiations, that resulted in a more
homogeneous skin redness.